Processor power delivery system

ABSTRACT

A system for delivering power to a processor enables a DC-to-DC converter substrate to be secured to the processor carrier in the Z-axis direction. The ability to assemble converter to the processor in this way facilitates assembly compared to systems in which the converter is plugged in to the processor carrier in the direction substantially parallel to the surface of the motherboard.

BACKGROUND

This invention relates generally to power delivery to electroniccircuits and particularly to an improved power delivery system forsupplying power from a power source to a processor.

In a typical computer system, a large printed circuit known as a“motherboard” contains a number of basic components. The motherboard issupplied with voltage from a power supply. The motherboard includesconnectors for daughter boards that can be plugged in to provideadditional capabilities. Such boards, for example, may provide aninterface to disk drives and compact disk read only memories, and mayprovide modem interfaces for local area networks and the like.

Processors operate at lower voltages than some other components on themotherboard. However, because of their high speed, processors consumelarge amounts of power despite the fact that they use lower voltages.Since the processor is operating at a low voltage with high power, thecurrent required by the processor is large. A localized DC-to-DCconverter (known as a voltage regulator module (VRM) or power pod)reduces the main supply voltage for supplying the processor, forexample. Typically for Intel 32 bit processors, this DC-to-DC converterplugs into a connector on the motherboard. The lower voltage is thenconducted through printed circuit traces on the motherboard to theprocessor socket. For higher current Intel 64 bit processors, theDC-to-DC converter connects directly to the processor package through anedge connector because of the high loss associated with conveying powerthrough two connectors and the motherboard as in Intel 32-bit systems.The power connector may also provide signal connections related to powersupply issues.

Conventionally, the processor is plugged into the motherboard in adirection that is transverse to the plane of the motherboard. If theplane of the motherboard defines the X and Y directions, the processoris plugged into the motherboard in the Z-axis direction. In other words,the processor is moved from a position above the motherboard downwardlyto plug into the motherboard. Conventionally, the DC-to-DC converter isplugged onto the processor package edge in a direction that is generallyparallel to the surface of the motherboard (transverse to the Z-axisdirection).

This configuration results in a number of difficulties. With theprocessor already attached to the motherboard, the action of pluggingthe converter into the processor carrier along the surface of themotherboard (e.g., the X-axis direction) is prone to interference fromupwardly directed components already on the motherboard. Moreover, thereis little room to manipulate the converter connections along themotherboard. The interconnection of the converter and the processorcarrier is awkward, increasing the demands on assembly workers andrequiring more elaborate interconnection devices. A complex rigid mountmechanism is used to align the processor package and the DC-to-DCconverter in both the Z and X axis. This takes up a large amount ofmotherboard real estate.

Thus, there is a need for an improved way of delivering power to aprocessor package edge.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side elevational view of one embodiment of the invention inthe course of assembly;

FIG. 2 is a top plan view of the embodiment shown in FIG. 1;

FIG. 3 is an enlarged, partial, bottom plan view of the DC-to-DCconverter substrate planar power contacts shown in FIG. 1;

FIG. 4 is a cross-sectional view taken generally along the line 4—4 inFIG. 2;

FIG. 5 is a partial exploded view of the embodiment shown in FIG. 4; and

FIG. 6 is a top plan view of a component shown in FIG. 5.

DETAILED DESCRIPTION

Referring to FIG. 1, a processor power delivery system 10 enables aDC-to-DC converter 12 to be assembled to a processor carrier 18 in theZ-axis. The Z-axis (indicated by an arrow in FIG. 1) is the directionthat is transverse to the surface of a motherboard 28 and transverse tothe lengths of the converter 12 and the processor carrier 18.

The processor carrier 18 may be plugged into a socket 50 that in turnplugs into a motherboard 28, all in the Z-axis direction. A processor 52may be attached on the carrier 18, for example using surface mountsolder balls 20, to a connection layer 21. Thereafter, the converter 12,including components 54, may plugged atop the processor carrier 18 alsoin the Z-axis direction. This greatly facilitates the connection of thetwo units.

The converter 12 includes contacts 16 on its lower surface 14 to makedirect surface to surface contact with the processor carrier 18. Thecontacts 16 communicate with the converter 12 components 54 through vias(not shown). The processor carrier 18 includes contacts 22 on its uppersurface that mate with the contacts 16 when the carrier 18 and converter12 are edge combined. The contacts 22 eventually electrically connect topower supply pins (not shown) on the processor 52 through connectionlayer 21. In one embodiment, the contacts 16 and 22 may each be formedof a copper land pattern.

A pair of upstanding alignment pins 24 a and 24 b on the processorcarrier 18 pass through holes (not shown in FIG. 1) in the converter 12.This pin/hole connection aligns the contacts 16 and 22 and facilitatesthe clamping engagement between the converter 12 and the processorcarrier 18.

Thus, referring to FIG. 2, the pins 24 a and 24 b pass completelythrough the converter 12 in one embodiment of the present invention.This engagement aligns the contacts 16 and 22 with respect to oneanother as the converter 12 is pressed down into firm engagement withthe processor carrier 18 in the Z-axis direction.

Referring to FIG. 4, the converter 12 laps over an edge and electricallyengages, in direct surface to surface contact, the processor carrier 18.The converter 12 and processor carrier 18 may be clamped together usingclamping devices 38 and clamping housing 58. In one embodiment of thepresent invention, the pins 24 may be threaded and may be secured usingthreaded fasteners. However, other clamping devices may be utilized tomaintain an even clamping force along the length of the contacts 16 and22.

Referring to FIG. 3, the contacts 16 of the converter 12 include a firstset of planar interdigitated contacts 16 a that may provide a powersupply (Vcc) connection. A second set of planar interdigitated contacts16 b may provide the ground (Vss) or return power connection. Theinterdigitation may be achieved through fingers 40, in one embodiment ofthe present invention. The interdigitation of the fingers 40 reduces theinductance of the power contacts 16 a and the ground contacts 16 b sincemutual inductance is cancelled out by the interdigitated arrangement.

Power control signals (such as a PWRG00D signal) may also pass throughthe contacts 16 from the contacts 22. For example, a plurality ofisolated power signal vias 34 may extend through the contacts 16.Similarly, vias 36 may pass through the process planar power contacts22. The arrangement of the signal vias 34 and 36 is subject toconsiderable variation.

Alignment holes 26 are provided on the converter 12 for engagement withthe alignment pins 24 on the processor carrier 18. The arrangement ofthe contacts 22 may be identical to that shown in FIG. 3 with theexception that the contacts 22 may include vias 36 to an internal copperland pattern (not shown) and may further include the vias 34 whichextend through the contacts 16 for conduction of other signals.

The processor power delivery system 10 may include a plurality ofcomponents that may be resiliently clamped together between the housing58 and the motherboard 28 as shown in FIG. 5. The housing 58 may includean upper surface with a plurality of reinforcing ribs 62 and a body 60.Formed in the body 60 is a corrugated spring 64. The ends 66 of thespring 64 may be held within the body 60 for example by molding thespring 64 into the body 60.

When the body 60 is pressed against the converter 12, the spring 64 veesare compressed, applying a uniform force through the body 60 to theconverter 12. In one embodiment, the spring 64 may be formed ofberyllium copper. It may be shaped in a corrugated shape with aplurality of vees extending into the spring 64 from above and below.Each of the vees may form a V-shaped compression spring pressed againsteither the body 60 or the converter 12. The arrangement of thecorrugated spring 64 serves to make more uniform the forces appliedthrough the body 60.

Ideally, the housing 58 supplies a substantially constant pressure overthe life of the system 10. The spring 64 may be defined with the coldflow properties of the related substrates over time in mind. The housing58 may be formed of extruded aluminum or plastic as two examples. In oneembodiment, the housing 58 may be hinged and latched to clear thecontact region and to allow for Z-axis assembly or replacement ofcomponents while providing a registration feature to align theunderlying substrates.

Sandwiched between the converter 12 and the processor carrier 18 is arelatively low profile conductive polymer interconnect 68 including apolymer film 70 having captured therein conductive polymer contacts 72.In one embodiment of the present invention, the film 70 may be formed ofkapton and the polymer contacts 72 may be formed of a polymer that hasbeen made conductive for example by doping it with conductive particlessuch as silver particles or oriented metallic wires. In each case, thepolymer contacts 72 may be formed of a plastic material that isrelatively resilient so that the material may be compressed between theconverter 12 and the carrier 18. The polymer contacts 72 produce aconductive contact between the converter 12 and the carrier 18.Moreover, because of the resilient nature of the interconnect 68,surface irregularities may be accounted for and more reliableinterconnection may be achieved in some cases.

In some embodiments, the conductive polymer contacts 72 may besubstantially thicker than the film 70. For example, in one embodiment,the contacts 72 may have a thickness four times that of the film 70.

As shown in FIG. 6, the interconnect 68 includes a pair of openings 74to receive and pass the alignment pins 24 a and 24 b. The alignment pins24 a and 24 b also act to precisely position the contacts 72 withrespect to the converter 12 and the carrier 18. The pins 24 a and 24 bmay extend upwardly through the interconnect 68 and the converter 12 andin one embodiment through the housing 58 for securement by securementdevices 38 shown in FIG. 4. In other cases, as mentioned previously, ahinged clamping device may be positioned for selectively applying aclamping force to the converter 12 and carrier 18 through the body 60and the spring 64.

The contacts 16 and 22 may be brought into direct, planar surface tosurface contact with one another. The contacts 16 and 22 may be broughtinto direct engagement in the Z-axis direction, with the converter 12atop the processor carrier 18. With the application of a compressionforce across the converter 12 and the processor carrier 18, goodelectrical contact may be obtained. The pins 56 on the socket 50 provideelectrical communication with the motherboard 28.

Because the converter 12 and the processor carrier 18 may both beassembled in the Z-axis direction, the assembly of the processor powerdelivery system 10 is facilitated. Of course, it is not necessary thateither the converter 12 or the processor carrier 18 be rigorously movedthrough the Z-axis direction. Instead, either or both of the converter12 and the processor carrier 18 may be moved so as to have a componentof displacement in the Z-axis direction relative to the plane of themotherboard 28. Since the contacts 16 and 22 meet along a common plane,the converter 12 may be moved onto the processor carrier 18 at any anglebetween the Z-axis and the plane of the motherboard 28.

The electrical performance may be optimized in some embodiments bymodifying the patterning of the contacts 16 and 22 without re-toolingconverter 12 or carrier 18 assemblies. Some embodiments may achieve amechanical benefit from having a single axis of assembly.

While an embodiment is illustrated in FIGS. 1 through 6 using planarcontacts, embodiments of the present invention may be applied to otherdesigns as well. The combination of the spring 64 and the interconnect68 may be particularly desirable because the pressure applied by thespring 64 may result in more even pressure applied to the conductivecontacts 72 in some embodiments.

In an embodiment using conductive polymer contacts captured in a kaptonfilm, the film may be formed by molding the conductive contacts into apreviously formed film, as one example. Another way of forming theinterconnect 68 includes shaking conductive contacts into holes in thefilm and then bonding the contacts in place. Generally, pressure may beapplied to the contacts to increase their conductivity.

While the present invention has been described with respect to a limitednumber of embodiments, those skilled in the art will appreciate numerousmodifications and variations therefrom. It is intended that the appendedclaims cover all such modifications and variations as fall within thetrue spirit and scope of this present invention.

What is claimed is:
 1. A device comprising: a DC-to-DC converter; a bodyhaving at least one side; and a compression spring retained on one sideof said body and clamped between said converter and said body such thatthe clamping force applied to said body may be resiliently spreadthrough said compression spring.
 2. The device of claim 1 wherein saidspring is corrugated.
 3. A motherboard comprising: a circuit board; aprocessor-carrier on said board; a DC-to-DC converter secured on saidcarrier; a housing including a compression spring positioned over saidconverter; and a clamp to clamp said housing, converter and carriertogether.
 4. The motherboard of claim 3 wherein said power and groundcontacts on each one of said converter and processor carrier areinterdigitated.
 5. The motherboard of claim 3 wherein said carriercontacts engage said board in a direction transverse to the plane ofsaid board.
 6. The motherboard of claim 3 wherein said converter isclamped onto said carrier.